Decontamination system

ABSTRACT

A decontamination system in combination with a work space maintained at subambient pressure. An inner vestibule is connected to the work space via a first portal, which can be selectively opened and closed by a first door. A middle vestibule, in which at least one shower bath is installed, is connected to the inner vestibule only via a second portal, which can be selectively closed by a second door or opened. An outer vestibule is connected to the middle vestibule only via a third portal, which can be selectively opened and closed by a third door, and to an ambient space only via a fourth portal, which can be selectively opened or closed by a fourth door. Each door is a rigid door. Except for the third door, which seals the third portal when the third portal is closed by the third door, each door has fixed louvers allowing small quantities of air to infiltrate. The third door is interconnected with the second door in such a manner, as by means of a chain of fixed length, that the second and third portals cannot be simultaneously opened. Personnel can leave their tools and garments in the inner vestibule, use the shower bath in the middle vestibule, and put on clean garments in the outer vestibule, from which they can pass to the ambient space, with minimal risk of escape of fugitive particles via the decontamination system.

BACKGROUND OF THE INVENTION

This invention pertains generally to a decontamination system for use bypersonnel working in a work space contaminated with airborne particles,such as asbestos particles, and particularly to such a decontaminationsystem in combination with such a work space.

For many years, asbestos insulation was used widely for its insulatingand fireproofing properties. However, recent findings of health hazardsassociated with airborne particles, particularly asbestos particles,have led to concerted efforts to remove asbestos insulation from publicbuildings and other structures. An important industry has been developedto deal with asbestos abatement.

Because of health hazards associated with asbestos particles, great caremust be taken to protect personnel working in asbestos abatement and toavoid escape of fugitive particles from the work space. The U.S.Environmental Protection Agency, the U.S. Occupational Safety and HealthAdministration, and other regulatory authorities and standard-settingagencies have developed detailed guidelines dealing with asbestosabatement.

Personnel working in asbestos abatement require a decontaminationsystem, in which they can change their garments and leave their tools.An example of such a system is disclosed in U.S. Pat. No. 4,604,111.

SUMMARY OF THE INVENTION

It is a principal object of this invention to provide a decontaminationsystem of an improved type, in combination with a work space, which isisolated by the decontamination system from an ambient space, and whichmay be contaminated with airborn particles, such as asbestos particles.The work space is maintained at subambient pressure, e.g., 0.02 to 0.04inches of water below ambient pressure, as by means of an air exhaustsystem equipped with an air filtering device.

In accordance with this invention, the decontamination system comprisesan inner vestibule, a middle vestibule, and an outer vestibule. Herein,each reference to a work space or to a vestibule is intended to refernot only to an enclosed space but also to its enclosing walls.

The inner vestibule is connected to the work space via and preferablyonly via a first portal. The decontamination system comprises a firstdoor, preferably a rigid door, which is mounted between the innervestibule and the work space so as to enable the first portal to beselectively opened and closed by the first door. The first door isadapted, as by means of fixed louvers, to allow small amounts of air toinfiltrate from the inner vestibule, through the first door, and intothe work space when the first portal is closed by the first door.

The middle vestibule is connected to the inner vestibule via andpreferably only via a second portal. The decontamination systemcomprises a second door, preferably a rigid door, which is mountedbetween the middle vestibule and the inner vestibule so as to enable thesecond portal to be selectively opened and closed by the second door.The second door is adapted, as by means of fixed louvers, to allow smallamounts of air to infiltrate from the middle vestibule, through thesecond door, and into the inner vestibule when the second portal isclosed by the second door. The decontamination system comprises at leastone shower bath installed in the middle vestibule for use by personnelentering the middle vestibule from the inner vestibule.

The outer vestibule is connected to the middle vestibule via andpreferably only via a third portal and is connected to the ambient spacevia and preferably only via a fourth portal. The decontamination systemcomprises a third door, preferably a rigid door, which is mountedbetween the outer vestibule and the middle vestibule so as to enable thethird portal to be selectively opened or closed by the third door. Thethird door is interconnected with the second door in such a manner thatthe second and third portals cannot be simultaneously opened. The thirddoor is adapted to seal the third portal against infiltration of airwhen the third portal is closed by the third door. The decontaminationsystem comprises a fourth door, preferably a rigid door, which ismounted between the ambient space and the outer vestibule so as toenable the fourth portal to be selectively opened and closed by thefourth door. The fourth door is adapted, as by means of fixed louvers,to allow small amounts of air to infiltrate from the ambient space,through the fourth door, and into the outer vestibule when the fourthportal is closed by the fourth door.

Personnel whose tools, bodies, and garments are contaminated can passfrom the work space, through the first portal, and into the innervestibule, in which they can leave their tools and their garments. Theycan pass from the inner vestibule, through the second portal, and intothe middle vestibule, in which they can use the shower bath. They canpass from the middle vestibule, through the third portal, and into theouter vestibule, in which they can put on clean garments. They can passfrom the outer vestibule, through the fourth portal, and into theambient space. Personnel seeking to enter the work space can passoppositely through the decontamination system. Personnel can passthrough the decontamination system with minimal risk of escape offugitive particles from the decontamination system.

These and other objects, features, and advantages of this invention willbe better understood from the following description of a preferredembodiment of this invention, with reference to the accompanyingdrawing.

BRIEF DESCRIPTION OF THE DRAWING

The drawing is a floor plan of a work space and a decontaminationsystem, as combined in a preferred embodiment of this invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

As shown in the drawings, a decontamination system 10 is combined with awork space 12, in such a manner as to constitute a preferred embodimentof this invention.

The work space 12, which is isolated by the decontamination system fromthe work space 12, and which may be contaminated with airborneparticles, such as asbestos particles, is maintained at subambientpressure, e.g., 0.02 to 0.04 inches of water below ambient pressure, bymeans of an air exhaust system including an air filtering device 14,which may include a HEPA filter. ("HEPA" is an acronym for "HighEfficiency Particulate Air".) The work space 12 may have a number offree-standing air filtering devices 16, two being shown, each of whichalso may include a HEPA filter, so as to filter fugitive particles fromthe air within the work space 12. Each such device 16 may be placed soas to direct filtered air at personnel working in the work space 12. Useof an air exhaust system equipped with an air filtering device has beenknown per se in asbestos abatement.

The work space 12 may have impermeable barriers (not shown), e.g.,plastic sheeting, at all inlets and outlets other than a first portalnoted below and on all decorative or other surfaces that cannot beeasily decontaminated. Widespread use of plastic sheeting, however, isnot necessary.

Broadly, the decontamination system comprises an inner vestibule 18,which may be also called a "dirty" room, a middle vestibule 20, in whichfour shower baths are installed, as indicated diagrammatically at 22,24, 26, and 28 respectively, and which may be also called a "shower"room, and an outer vestibule 30, which may be also called a "clean"room. The inner vestibule 18, the middle vestibule 20, and the outervestibule 30 are sealed, except as noted below.

The inner vestibule 18 is connected to the work space 12 only via afirst portal 32. The decontamination system 10 comprises a first door34, which is a rigid door, and which is mounted between the innervestibule 18 and the work space 12 so as to enable the first portal 32to be selectively opened and closed by the first door 34. The first door34 is provided with fixed louvers 36, as shown diagrammatically, whichallow small amounts of air to infiltrate from the inner vestibule 18,through the first door 34, and into the work space 12 when the firstportal 32 is closed by the first door 34.

The middle vestibule 20 is connected to the inner vestibule 18 only viaa second portal 38. The decontamination system 10 comprises a seconddoor 40, which is a rigid door, and which is mounted between the middlevestibule 20 and the inner vestibule 18 so as to enable the secondportal 38 to be selectively opened and closed by the second door 40. Thesecond door 40 is provided with fixed louvers 42, as showndiagrammatically, which allow small amounts of air to infiltrate fromthe middle vestibule 20, through the second door 40, and into the innervestibule 18 when the second portal 38 is closed by the second door 40.

The outer vestibule 30 is connected to the middle vestibule 20 only viaa third portal 44 and is connected to the ambient space only via afourth portal 46. The decontamination system 10 comprises a third door,which is a rigid door, and which is mounted between the outer vestibule30 and the middle vestibule 20 so as to enable the third portal 44 to beselectively opened and closed by the third door 48. The third door 48 isinterconnected with the second door 40 in such a manner that the secondportal 38 and the third portal 44 cannot be simultaneously opened. Thethird door 48 is adapted by means of peripheral gaskets (not shown) orotherwise to seal the third portal 44 against infiltration of air whenthe third portal 44 is closed by the third door 48. The decontaminationsystem 10 comprises a fourth door 50, which is a rigid door, and whichis mounted between the ambient space and the outer vestibule 30 so as toenable the fourth portal 46 to be selectively opened and closed by thefourth door 50. The fourth door 50 is provided with fixed louvers 52, asshown diagrammatically, which allow small amounts of air to infiltratefrom the ambient space, through the fourth door 50, and into the outervestibule 30 when the fourth portal 46 is closed by the fourth door 50.

As shown diagrammatically, a chain 54 of fixed length is used tointerconnect the third door 48 with the second door 40. The chain 54 maybe so connected as to enable someone easily to disconnect the chain 54in an emergency. Desirably, an alarm (not shown) will sound if the chain54 is disconnected. In alternative embodiments (not shown) a cable offixed length, a rod of fixed length, or springs, spring loaded hinges orother door closing devices to interlock or to assure normally closedpositions of the second and third doors, or electromechanical meansinterlocking the third door 48 with the second door 40 so as to providea similar function may be so used.

Although the doors noted above are shown diagrammatically to be hingedand to be openable unidirectionally, sliding, rolling, or swinging doorsmay be alternatively used.

Personnel whose tools, and garments are contaminated can pass from thework space 12, through the first portal 32, and into the inner vestibule18, in which they can leave their tools and garments. They can pass fromthe inner vestibule 18, through the second portal 40, and into themiddle vestibule 20, in which they can use the shower baths 22, 24, 26,and 28. They can pass from the middle vestibule 20, through the thirdportal 44, and into the outer vestibule 30, in which they can put onclean garments. They can pass from the outer vestibule 30, through thefourth portal 46, and into the ambient space. Personnel seeking to enterthe work space 12 can pass oppositely through the decontaminationchamber 10.

When the third portal 44 is opened, a limited amount of air tends toflow from the outer vestibule 30 into the middle vestibule 20, from themiddle vestibule 20 into the inner vestibule 18, and from the innervestibule 18 into the work space 12, from which air is exhausted by theair exhaust system through the air filtering device 14. Thus, personnelcan pass through the decontamination system 10 with minimal risk ofescape of fugitive particles from the decontamination system 10.

HEPA filters (not shown) which allow air to flow as described in thepreceding paragraph, but which do not allow fugitive particles to passoppositely may be installed in the third door 38, or in its adjacentwall between vestibule 20 and vestibule 30 or may be used in place ofone or more of the louvers 36, 42, and 46 or in suitable apertures (notshown) in the adjacent walls which respectively divide the innervestibule 18 from the work space 12, the middle vestibule 20 from theinner vestibule 18, and the outer vestibule 30 from the ambient space.Exfiltration of fugitive particles would be thus minimized, even if theair exhaust system including the air filtering device 14 were to fail.

The inner vestibule 18 may be also equipped with toilet facilities (notshown) and with tool and garment storage and cleaning facilities (notshown). The middle vestibule 20 may be so arranged that personnel cannotbypass the shower baths 22, 24, 26, and 28. The outer vestibule 30 maybe also equipped with garment lockers (not shown) and other conveniencesfor personnel using the decontamination system 10. As desired or needed,other additions may be also made to the decontamination system 10.

The decontamination system 10 operates in a way that is vastly differentfrom what has been in widespread use in the asbestos abatement industry.The decontamination system 10 alleviates serious concerns over anyapproach that indiscriminately calls for removal of large amounts ofanything, even air, from a contaminated work space. HEPA filter failure,machine cabinet leakage, filter seal leakage, and exhaust duct breakthrough a venturi effect, among other possibilities, can provide escaperoutes for fugitive airborne asbestos to the outside world. Since theremoval of each unit volume from such a work space is a potentialasbestos contaminant vehicle, it makes good sense to minimize such flowrather than maximize it, at least from a contingency standpoint.

The decontamination system 10 does not establish flow paths, except asdescribed above, provide flap seals, require air exhaust periodicity, oreven necessarily call for widespread use of plastic sheeting. The basicstrategy embodied in the decontamination system 10 is (a) to seal allpotential air paths in the work space as tightly as possible, (b) toprovide a filtered exhaust system which removes only enough air from thesealed, isolated work space to establish a lower pressure and to offsetany air leakage, and (c) to provide additional engineering controls tolower airborne fiber content within the work space. The engineeringcontrols include a suitable number of HEPA filter devices 16, thecapacity of which, combined with the capacity of device 14, aresufficient to cleanse the air internally of the work space 12 as manytimes an hour as may be desired or specified.

I claim:
 1. In combination with a work space, which may be contaminatedwith airborne particles, such as asbestos particles, and which ismaintained at subambient pressure, a decontamination system isolatingthe work space from an ambient space and comprising:(a) an innervestibule, which is connected to the work space via a first portal; (b)a first door, which is mounted between the inner vestibule and the workspace so as to enable the first portal to be selectively opened andclosed by the first door, and which is adapted to allow small amounts ofair to infiltrate from the inner vestibule, through the first door, andinto the work space when the first portal is closed by the first door;(c) a middle vestibule, which is connected to the inner vestibule via asecond portal; (d) a second door, which is mounted between the middlevestibule and the inner vestibule so as to enable the second portal tobe selectively opened and closed by the second door, and which isadapted to allow small amounts of air to infiltrate from the middlevestibule, through the second door, and into the inner vestibule whenthe second portal is closed by the second door; (e) at least one showerbath installed in the middle vestibule for use by personnel entering themiddle vestibule from the inner vestibule; (f) an outer vestibule, whichis connected to the middle vestibule only via a third portal, and whichis connected to the ambient space via a fourth portal; (g) a third door,which is mounted between the outer vestibule and the middle vestibule soas to enable the third portal to be selectively opened and closed by thethird door, and which is interconnected with the second door in such amanner that the second and third portals cannot be simultaneouslyopened, and which is adapted to seal the third portal againstinfiltration of air when the third portal is closed by the third door;(h) a fourth door, which is mounted between the ambient space and theouter vestibule so as to enable the fourth portal to be selectivelyopened and closed by the fourth door, and which is adapted to allowsmall amounts of air to infiltrate from the ambient space, through thefourth door, and into the outer vestibule when the fourth portal isclosed by the fourth door;whereby personnel whose tools, and garmentsare contaminated can pass from the work space, through the first portal,and into the inner vestibule, in which they can leave their tools andgarments, from the inner vestibule, through the second portal, and intothe middle vestibule, in which they can use the shower bath, from themiddle vestibule, through the third portal, and into the outervestibule, in which they can put on clean garments, and from the outervestibule, through the fourth portal, and into the ambient space, withminimal risk of escape of fugitive particles from the work space via thedecontamination system.
 2. The combination of claim 1 wherein each dooris a rigid door.
 3. The combination of claim 2 wherein, except for thethird door, each door has fixed louvers allowing air to infiltratethrough such louvers.
 4. The combination of claim 1 wherein the workspace contains at least one free-standing air-filtering device.
 5. Thecombination of claim 4 wherein the work space contains at least twofree-standing air-filtering devices.